This application addresses broad Challenge Area (11) Regenerative Medicine and specific Challenge Topic, 11-DK-101: Promote regeneration and repair in the digestive system, liver, pancreas, kidneys, hematologic, and urologic system. Chronic kidney disease (CKD) is a serious global health problem associated with significant morbidity and mortality. Complete loss of kidney function results in end-stage renal disease (ESRD), and renal replacement therapies such as dialysis and transplantation are required to sustain life. Given the complications that are associated with these treatment modalities, cell-based strategies focused on replacing the cells that are lost in CKD and regenerating kidney tissue represent an innovative approach to treating CKD. Human inducible pluripotent stem (iPS) cells, a powerful and rapidly evolving technology in the field of regenerative medicine, could serve as a virtually unlimited patient-specific source of starting material for regenerating human kidney tissue. Currently, there are no existing protocols to generate renal epithelial cells from human iPS cells, embryonic stem (ES) cells, or any other cell type. The ultimate goal of the work proposed is to develop a stepwise protocol for the differentiation of human iPS cells into renal progenitor cells. A distinct population of renal progenitor cells could serve as a starting point for subsequent differentiation of glomerular and tubular epithelial cells. We will address this challenge with a two-step approach. In our first specific aim, we will use mouse reporter gene models in a high-throughput system to screen libraries of small molecules for candidates that can drive the differentiation of mouse ES cells towards a renal progenitor cell fate. The activation of the reporter genes odd-skipped related 1 (Osr1) and Six2 by small molecules will signify the successful differentiation of mouse ES cells into renal progenitor cells from the intermediate mesoderm, the precursor to all kidney tissue, and the metanephric mesenchyme, respectively. The identification of key small molecules would represent the first step in producing desired renal epithelial cells from ES cells. We will also explore the ability of other non-renal epithelial cells such as hepatocytes to be reprogrammed by small molecules into renal progenitor cells. In our second specific aim, we will establish a set of conditions whereby human iPS cells can be differentiated into renal progenitor cells in vitro. The effectiveness of small molecules, developmental transcription factors, exogenous growth factors, and extracellular matrix materials to induce the renal progenitor cell fate will be evaluated. We will also determine if adult mouse kidney proximal tubular cells can be reprogrammed into iPS cells and whether this reprogramming process involves reactivation of the kidney developmental genes Osr1 and Six2. Populations of human iPS cell-derived renal epithelial cells would be novel and important for multiple translational applications, including 1) incorporation into 3D structures to construct kidney tubules, as a first step to bioengineering patient-specific kidney tissue, 2) incorporation into renal assist devices to treat patients with severe forms of kidney injury, 3) development of in vitro models of patient-specific kidney diseases, and 4) the development of kidney-specific efficacy and toxicity screens for potential therapeutics. PUBLIC HEALTH RELEVANCE: Chronic kidney disease (CKD), the gradual and usually permanent loss of kidney function over time, is a significant worldwide public health problem affecting approximately 8-9% of the population over 40 years of age in the developed world. This is associated with very high cardiovascular mortality and is a great financial burden as patients progress to end stage renal disease and require dialysis or transplantation. Although recent advances in stem cell research have given hope to the use of human stem cells in the treatment of many human diseases, it is very important to understand how stem cells and kidney progenitors can be used to treat kidney disease. The purpose of this study is to develop strategies for transforming stem cells into cells of the kidney, with the ultimate goal of regenerating kidney tissue to treat patients with CKD.